共查询到20条相似文献,搜索用时 15 毫秒
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GAO Jie 《中国物理C(英文版)》2009,33(4):306-310
In this paper we give a set of analytical formulae to describe the characteristics of photocathode rf guns at any rf frequencies, such as energy, energy spread, bunch length, out going current, and emittance etc.as functions of the laser injection phase, which are useful in the design and practical operation of rf guns. 相似文献
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Heishun Zen Toshiteru Kii Kai Masuda Hideaki Ohgaki Tetsuo Yamazaki 《Infrared Physics & Technology》2008,51(5):382-385
A mid-infrared free electron laser (FEL) has been constructed for energy science in the Institute of Advanced Energy, Kyoto University. The FEL system consists of a compact S-band Linac and an undulator to generate 4–13 μm coherent mid-infrared radiations. The Linac consists of a 4.5 cell rf gun with a thermionic cathode and a 3-m traveling-wave-type accelerator tube fed by 10 MW and 20 MW rf power, respectively. We have succeeded to produce 40 MeV, 40 mA and 3 μs electron beams. Last December, the 9.2 μm spontaneous emission from the undulator generated by 29.5 MeV electron beams was observed for the first time. Further optimization parameters of both the electron beam and the optical cavity are being pursued for an FEL lasing in the near future. 相似文献
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We consider a scheme to generate a sub-picosecond electron bunch in the photocathode rf gun by im-proving the acceleration gradient in the gun, suitably tuning the bunch charge, the laser spot size and the acceleration phase, and reducing the growth of transverse emittance by laser shaping. A nondestructive technique is also reported to measure the electron bunch length, by measuring the high-frequency spectrum of wakefield radiation which is caused by the passage of a relativistic electron bunch through a channel surrounded by a dielectric. 相似文献
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Narrow-band THz coherent Cherenkov radiation can be driven by a subpicosecond electron bunch trav- eling along the axis of a hollow cylindrical dielectric-lined waveguide. We present a scheme of compact THz radiation source based on the photocathode rf gun. On the basis of our analytic result, the subpicosecond electron bunch with high charge (800 pC) can be generated directly in the photocathode rf gun. According to the analytical and simulated results, a narrow emission spectrum peaked at 0.24 THz with 2 megawatt (MW) peak power is expected to gain in the proposed scheme (the length of the facility is about 1.2 m). 相似文献
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Narrow-band THz coherent Cherenkov radiation can be driven by a subpicosecond electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. We present a scheme of compact THz radiation source based on the photocathode rf gun. On the basis of our analytic result, the subpicosecond electron bunch with high charge (800 pC) can be generated directly in the photocathode rf gun. According to the analytical and simulated results, a narrow emission spectrum peaked at 0.24 THz with 2 megawatt (MW) peak power is expected to gain in the proposed scheme (the length of the facility is about 1.2 m). 相似文献
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The photoreflectance (PR) spectroscopy has been applied to investigate the band-gap energy (Eg) of indium nitride (InN) thin films grown by rf magnetron sputtering. A novel reactive gas-timing technique applied for the sputtering process has been successfully employed to grow InN thin films without neither substrate heating nor post annealing. The X-ray diffraction (XRD) patterns exhibit strong peaks in the orientation along (0 0 2) and (1 0 1) planes, corresponding to the polycrystalline hexagonal-InN structure. The band-gap transition energy of InN was determined by fitting the PR spectra to a theoretical line shape. The PR results show the band-gap energy at 1.18 eV for hexagonal-InN thin films deposited at the rf powers of 100 and 200 W. The high rf sputtering powers in combination with the gas-timing technique should lead to a high concentration of highly excited nitrogen ions in the plasma, which enables the formation of InN without substrate heating. Auger electron spectroscopy (AES) measurements further reveal traces of oxygen in these InN films. This should explain the elevated band-gap energy, in reference to the band-gap value of 0.7 eV for pristine InN films. 相似文献
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北京自由电子激光装置的设计研究 总被引:4,自引:2,他引:2
北京自由电子激光装置(BFEL)是一台工作在中红外区的康普顿型FEL振荡器。由一台30MeV的射频电子直线加速器提供电子束。特点之一是用微波电子枪作为高亮度注入器。本文首先概述了BFEL的一般情形和物理参数.接着用解析公式和模拟的方法论证了电子束的设计目标和激光器的运转特征。最后阐述了BFEL各部分采取的技术路线的特点,内容包括微波枪、加速器和微波系统、调制器、输运系统、摇摆磁铁、光学腔、电子束诊断、准直、自发辐射和激光实验。 相似文献
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A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges. 相似文献
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A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges. 相似文献
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Simulation of dielectric resonator for high-Tc radio frequency superconducting quantum interference device 下载免费PDF全文
Nowadays, the high-critical-temperature radio frequency
superconducting quantum interference device (high-$T_{\rm c }$ rf
SQUID) is usually coupled to a dielectric resonator that is a
standard $10\times 10\times 1$~mm3 SrTiO$3 (STO) substrate
with a YBa2Cu$3O$_{7 - \delta }$ (YBCO) thin-film flux
focuser deposited on it. Recently, we have simulated a dielectric
resonator for the high-$T_{\rm c }$ rf SQUID by using the ANSOFT High
Frequency Structure Simulator (ANSOFT HFSS). We simulate the
resonant frequency and the quality factor of our dielectric
resonator when it is unloaded or matches a 50-$\Omega$ impedance.
The simulation results are quite close to the practical
measurements. Our study shows that ANSOFT HFSS is quite suitable for
simulating the dielectric resonator used for the high-$Tc rf
SQUID. Therefore, we think the ANSOFT HFSS can be very helpful
for investigating the characteristics of dielectric resonators for
high-$Tc rf SQUIDs. 相似文献
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V. N. Manuilov T. Idehara M. Yu. Glyavin Information not available LaAgusu M. Kamada T. Kanemaki Wiehua Jiang K. Yatsui 《International Journal of Infrared and Millimeter Waves》2005,26(1):15-28
Short-pulse powerful Large Orbit Gyrotron with total electron energy about 400 kV and beam power in the cavity up to 100 MW is now under developing at FIR FU. Suitable for 200 ns pulse duration electron-optic system is analyzed. Results of numerical simulation for explosion emission cusp-type electron guns and magnetic field intensity about 8 T are presented. Sensitivity of the guns to small deviations from the nominal operating regime is investigated. Some versions of the gun with different accelerating potential as well as different beam current passing through the cavity (60-300A) are suggested. Current reduction simplifies the problems of mode competition and potential depression in the cavity, but at the same time decrease output power. To diminish current special diaphragms are suggested. Results of numerical simulation of collector corresponding to each version of the gun design including power density distributions along its surface are presented. It is shown that beam quality and collector regimes are suitable for LOG operation. 相似文献
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本文用含时多态展开方法计算了里德堡钾原子在静电场、微波场和低射频场[a radio-frequency(rf)field]共同作用下方波振荡的激发特性.研究计算了通过改变微波场的频率、振幅和静电场的振幅以及用低射频锯齿波代替低射频余弦波后方波振荡的变化,获得了一些非常有趣的结果,并给出了理论解释. 相似文献
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本文概述了在KT-5C托卡马克上研究非线性离子伯恩斯坦波用的新型射频波功率发射系统,给出了工作频率选择和稳定、射频功率的传输调节、脉冲响应、耦合网络及其阻抗变换、移动式天线等实验结果,还给出了测量天线真空负载阻抗的一种简便方法,讨论了有关结果。 相似文献